release search task in time (#3609)

Signed-off-by: shengjun.li <shengjun.li@zilliz.com>

CHANGELOG.md

@@ -4,6 +4,7 @@ Please mark all change in change log and use the issue from GitHub
 
 # Milvus 0.10.3 (TBD)
 ## Bug
+-   \#3536 Release search task in time to avoid excessive memory usage
 
 ## Feature
 -   \#3213 Allow users to specify a distance type at runtime for Flat index

core/src/scheduler/resource/Resource.cpp

@@ -12,6 +12,7 @@
 #include "scheduler/resource/Resource.h"
 #include "scheduler/SchedInst.h"
 #include "scheduler/Utils.h"
+#include "scheduler/task/FinishedTask.h"
 
 #include <iostream>
 #include <limits>
@@ -116,8 +117,9 @@ Resource::pick_task_load() {
     auto indexes = task_table_.PickToLoad(10);
     for (auto index : indexes) {
         // try to set one task loading, then return
-        if (task_table_.Load(index))
+        if (task_table_.Load(index)) {
             return task_table_.at(index);
+        }
         // else try next
     }
     return nullptr;
@@ -172,6 +174,7 @@ Resource::loader_function() {
             task_item->Loaded();
             if (task_item->from) {
                 task_item->from->Moved();
+                task_item->from->task = FinishedTask::Create(task_item->from->task);
                 task_item->from = nullptr;
             }
             if (subscriber_) {
@@ -201,6 +204,7 @@ Resource::executor_function() {
             }
             auto start = get_current_timestamp();
             Process(task_item->task);
+            task_item->task = FinishedTask::Create(task_item->task);
             auto finish = get_current_timestamp();
             ++total_task_;
             total_cost_ += finish - start;

core/src/scheduler/task/FinishedTask.cpp

@@ -0,0 +1,35 @@
+// Copyright (C) 2019-2020 Zilliz. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance
+// with the License. You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software distributed under the License
+// is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
+// or implied. See the License for the specific language governing permissions and limitations under the License.
+
+#include "scheduler/task/FinishedTask.h"
+
+namespace milvus::scheduler {
+
+std::shared_ptr<FinishedTask>
+FinishedTask::Create(const TaskPtr& task) {
+    return std::make_shared<FinishedTask>(task);
+}
+
+FinishedTask::FinishedTask(const TaskPtr& task) : Task(TaskType::SearchTask, nullptr) {
+    Task::task_path_ = task->task_path_;
+    Task::type_ = task->type_;
+    Task::label_ = task->label_;
+}
+
+void
+FinishedTask::Load(LoadType type, uint8_t device_id) {
+}
+
+void
+FinishedTask::Execute() {
+}
+
+}  // namespace milvus::scheduler

core/src/scheduler/task/FinishedTask.h

@@ -0,0 +1,35 @@
+// Copyright (C) 2019-2020 Zilliz. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance
+// with the License. You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software distributed under the License
+// is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
+// or implied. See the License for the specific language governing permissions and limitations under the License.
+
+#pragma once
+
+#include "scheduler/task/Task.h"
+
+#include <memory>
+
+namespace milvus::scheduler {
+
+class FinishedTask : public Task {
+ public:
+    static std::shared_ptr<FinishedTask>
+    Create(const TaskPtr& task);
+
+ public:
+    explicit FinishedTask(const TaskPtr& task);
+
+    void
+    Load(LoadType type, uint8_t device_id) override;
+
+    void
+    Execute() override;
+};
+
+}  // namespace milvus::scheduler

core/src/scheduler/task/SearchTask.cpp

@@ -314,7 +314,6 @@ XSearchTask::Execute() {
                     }
                 }
                 search_job->SearchDone(index_id_);
-                index_engine_ = nullptr;
                 return;
             }
             if (!vectors.float_data_.empty()) {
@@ -366,9 +365,6 @@ XSearchTask::Execute() {
     }
 
     rc.ElapseFromBegin("totally cost");
-
-    // release index in resource
-    index_engine_ = nullptr;
 }
 
 void